This application claims the priority of German application 197 13 089.5-26 filed in Germany on Mar. 27, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method for controlling and monitoring the cutting function of a thread cutter driven by an electric motor in looms, said thread cutter having a stationary part and a movable cutter part which performs a cutting movement.
From the German patent 40 00 856 A1, a thread cutter is known for cutting the inserted filling thread in looms. Here, the cutter is mechanically coupled with the main drive of the loom by a cam mechanism, or the like. The thread cutter operates synchronously with the rhythm of the machine. The moment (timing) of the cutting is therefore predetermined in a fixed manner with respect to the weaving cycle and is not variable or is variable only by major mechanical conversions.
A substantially more flexible thread cutter for filling threads is known from EP 0 284 766 B1. That thread cutter has a drive, which is independent of the main drive, so that the time of the cutting process can be predetermined as desired with respect to the weaving cycle by means of a programmable control unit. The drive includes a stepping motor having a shaft drivingly connected with a movable knife, which stepping motor is alternatively rotationally driven back and forth.
The alternating forward and backward rotation of the motor shaft, however, has the disadvantage that the stepping motor is exposed to high stresses and high wear by the continuous accelerating and decelerating processes. Furthermore, no monitoring of the thread cutter for damage thereto is provided.
An object of the invention is to provide an improved method for controlling and monitoring the cutting function of a thread cutter, which is driven by an electric motor, and serves for the cutting off of selvage while permitting a great flexibility in performing the cutting function and use under many different mechanical circumstances and in a diversity of places.
Another object of the invention is to increase the service life of the cutter drive and to provide a monitoring of the function of the thread cutter and of damage to it.
These and other objects are achieved according to preferred embodiments of the present invention by providing a method and apparatus for controlling and monitoring the cutting function of electromotively driven thread cutters in looms, having a main shaft driven in rotation, the cutter drive being an electric drive motor with a programmable electronic control unit, which is connected in signal-transmitting manner with a loom control, wherein, upon rotation of the motor shaft of the drive motor, at least one electric signal is produced and the electric signal is communicated to the loom control via the control electronics, and upon absence of the signal, the weaving process is interrupted.
Preferred embodiments of the invention have the advantage that, for instance, the motor of a selvage cutter can be driven continuously in one direction of rotation during the operation of the thread cutter and need not pass through starting and stopping cycles. This increases the service life of the motor.
The speed of rotation of the motor, and thus the cutting cycle and cutting time, are controlled and monitored by an electronic control mechanism according to preferred embodiments of the invention. The electronic control mechanism is advantageously integrated into the machine control and can be programmed via the control panel.
In certain preferred embodiments of the invention, rotation of the motor shaft is monitored by a monitoring device in the form of a sensor. In this connection, a magnetic receiver (Hall sensor) is preferably used, because of the surrounding conditions. Embodiments are also contemplated which use optical, capacative, inductive or other monitors, dependent on the specific conditions. By this type of monitoring, defects of the drive motor as well as breakage or jamming of the movable cutter part of the thread cutter can advantageously be detected.
In order to increase the service life of the thread cutter, according to certain preferred embodiments of the invention, provisions are made so that the speed of rotation of the motor shaft of the cutter motor can be operated at any adjustable ratio to the speed of rotation of the motor shaft of the loom drive. This means that, in the case of a fabric of relatively high filling density, the thread cutter cuts for instance in a ratio of 1:5 to the filling insertion (pick). In other words, after each filling insertion process, there is a single cutting for several filling threads, which are bound in the fabric and a selvage. Therefore, the filling threads of in each case the last five picks are cut between the fabric and the selvage.
There is furthermore the advantage of preferred embodiments of the invention that, depending on the filling material and the weaving design, different ratios of speed of rotation may also exist during repeat weavings with high pick density.
The inventive thread cutter is intended, in particular, for cutting off selvages since, as a result of the predeterminable ratio of speed of rotation of the cutter drive to the main shaft drive of the loom, several picks which have already been entered, can in advantageous fashion be cut by a single cutting process.
Due to the great flexibility in mounting and control, the thread cutter assembly according to certain preferred embodiments of the invention can be used just as well as a separate central cutting device for cutting a fabric web in the direction opposite the weaving direction for cutting each individual pick entered.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.